1. Field of the Invention
The present invention relates to an inspection method to enable a simple and easy inspection of an electrical connecting state between a connecting terminal of a semiconductor integrated circuit formed over a substrate and a connecting terminal of a FPC (Flexible Printed Circuit), and an inspection of an electrical connecting state between all terminals.
2. Description of the Related Art
In recent years, since a thin panel has low power consumption, a small size, and a light weight, the thin panel is incorporated into various electronic equipment and products. The thin panel has a semiconductor integrated circuit formed over a substrate such as a glass substrate or a plastic substrate. The semiconductor integrated circuit has to be connected with an external device, and a flexible printed circuit is usually used for the connection. Connection using a flexible printed circuit has advantages in that miniaturization, reduction in weight, and a three-dimensional wiring are possible.
Electrical connection of a connecting terminal of a semiconductor integrated circuit formed over a substrate and a crimp connecting terminal of a flexible printed circuit is performed by thermocompression using an anisotropic conductive film having an adhesive and a conductive particle. Thermocompression is the connection by heating treatment and pressurization treatment, here. When pressure is unevenly applied to a connected portion in the process of thermocompression, the flexible printed circuit is out of alignment and poor connection is sometimes occurred between the connecting terminal and the crimp connecting terminal. Therefore, it is necessary to inspect the electrical connecting state between the connecting terminal and the crimp connecting terminal. An inspection of the electrical connecting state can be performed by measuring a resistance value between the connecting terminals.
However, since the semiconductor integrated circuit is minute and a thin film, it is highly possible that wires are cut when connecting a terminal of an inspection device to the semiconductor integrated circuit over the substrate. Furthermore, when the substrate is a plastic substrate, a terminal of the inspection device cannot be fixed since the plastic substrate is soft.
As a conventional inspection method, there is a method in which a pad or a wire for the inspection is arranged over a substrate or an external device (for example, see Patent Documents 1 and 2).
[Patent Document 1]
Japanese Patent Laid-Open No. 2004-95872
[Patent Document 2]
Japanese Patent Laid-Open No. 2005-69945
It has been difficult to inspect the electrical connecting state between all terminals in the conventional inspection method which arranges a wire or a pad for inspection over a substrate or in an external device. For example, in the inspection method disclosed in Patent Document 1, an exclusive wire for inspecting the electrical connecting state between terminals is arranged besides a wire which is necessary for a circuit. Then, the exclusive wire is connected with a wire or a pad for inspection, and the inspection is performed only to see the electrical connecting state between the terminals. Here, when a wire which is necessary for the circuit and a wire or a pad for inspection are connected, electrical connection between the terminals can be inspected. However, in this case, when the circuit is operated, the wire or the pad for inspection becomes an obstacle. Therefore, it is necessary to cut the wire by using a device such as a laser cutter.
In addition, when a liquid crystal display panel is considered as an example of a thin panel, it is difficult to arrange a mensurative probe in a connecting terminal formed over the substrate after filling a liquid crystal material. Therefore, it has been necessary to inspect the connecting state by displaying a panel after filling the liquid crystal material. Needless to say, in thin panels other than the liquid crystal display panel, it is also difficult to arrange a mensurative probe in a connecting terminal formed over a substrate in the same manner after sealing by a counter substrate or after forming a protective film or the like to inspect the connection state.